Wireless communication system, base station apparatus, mobile station apparatus, and communication method

ABSTRACT

TPC is appropriately operated in response to access method switching timing, an error is prevented from occurring in communication, and influence given to another cell due to transmission of unnecessary power is reduced. 
     A base station apparatus which performs wireless communication with a mobile station apparatus while switching a plurality of kinds of communication method, transmits control information for performing transmit power control of the mobile station apparatus to the mobile station apparatus. The mobile station apparatus receives the control information for performing the transmit power control from the base station apparatus and determines a transmitted power according to the control information when switching the communication method.

TECHNICAL FIELD

The present invention relates to a technique of performing wirelesscommunication while switching plural kinds of communication method.

BACKGROUND ART

In the conventionally known wireless communication technique, an uplink(also called upstream or upstream link) generally means a linktransmitting data from a mobile station apparatus to a base stationapparatus when communication is performed between the base stationapparatus and the mobile station apparatus in cellular communication orthe like. In this uplink, the base station apparatus receives signalsfrom various mobile station apparatuses at the same time. Thereby, whenreceived power is the same among the signals, reception process iseasily performed and an excellent reception characteristic is obtained.For realizing this condition, there is introduced a system ofcontrolling a transmitted power of a signal transmitted from the mobilestation apparatus, which is called transmit power control (TPC).

The communication method used for a mobile phone of 3G (thirdgeneration) is CDMA (Code Division Multiple Access), and the pluralmobile station apparatuses use respective codes different form oneanother and access the base station apparatus using the same frequency,and thereby the TPC is generally required to have a high accuracy and ahigh speed. Meanwhile, in a standard of the mobile phone for the nextgeneration (3.9G), DFT-S-OFDMA (Discrete FourierTransform-Spread-Orthogonal Frequency Division Multiple Access) is to beused as an uplink communication method, in which the TPC is not requiredto have a high accuracy and a high speed as in the TPC used in CDMA butthe TPC is specified for the purpose of appropriately controllinginterference to a neighboring base station apparatus (Non-patentdocument 1).

TPC methods are broadly divided into two and called an open loop and aclosed loop, respectively. In an brief explanation assuming the use ofthe TPC in the uplink, the TPC of the open loop is a control method inwhich the mobile station apparatus controls the transmitted power byjudgment of the mobile station apparatus and the TPC of the closed loopis a control method in which the transmitted power is controlled by aninstruction from the base station apparatus.

In the open loop, there is a method in which an attenuation amount isestimated by the use of transmitted power transmitted from the basestation apparatus and received power actually received by the mobilestation apparatus, and transmitted power of the mobile station apparatusis determined from the estimated attenuation amount and received powerrequired by the base station apparatus. Meanwhile, in the closed loop,there are a method in which the base station apparatus measures thereceived power and notifies a short or over amount thereof and a methodin which the base station apparatus notifies increase or decrease of thetransmitted power in the mobile station apparatus by the use of an errorrate of a transmitted signal or the like.

PRIOR ART DOCUMENT Non-Patent Document

Non-patent document 1: 3gpp is 36.213 v8. c 5. 0 5.1

DISCLOSURE OF THE INVENTION Problem to be Solved by the Invention

However, for the generation after next (4G), as an uplink communicationmethod, it is being discussed that plural access methods are switchedtherebetween to be used. The specifically discussed access methods areDFT-S-OFDMA (also called SC-FDMA) which uses continuous subcarriers,Clustered DFT-S-OFDMA which uses non-continuous subcarriers, and furtherOFDMA. Moreover, as a method for switching these access methodstherebetween, semi-static switching, that is, a method using the samemethod for a comparatively long time as far as there is not a largemovement of the mobile station apparatus, and dynamic switching, thatis, a method of switching the access methods therebetween by a packetunit, are being discussed.

When the access method is changed, required received power becomesdifferent and maximum transmitted power to be transmitted becomesdifferent. If the TPC used in 3.9G is applied to 4G without change,there arises a problem in such a system that the received power requiredby the base station apparatus cannot be secured and data error is causedat the instant of the switching. Further, there also arises a problemthat the mobile station apparatus transmits unnecessarily large powerand gives interference to another cell.

The present invention has been achieved in view of such a situation andhas an object of providing a wireless communication system, a basestation apparatus, a mobile station apparatus, and a communicationmethod, which can operate the TPC appropriately in response to switchingtiming of the access method to prevent an error from occurring incommunication and can reduce influence given to another cell due to thetransmission of unnecessary power.

Means for Solving the Problem

(1) For achieving the above object, the present invention is configuredas follows. That is, a wireless communication system of the presentinvention, in which a transmission apparatus and a reception apparatusboth capable of using plural kinds of communication method performwireless communication while switching the transmission method, performstransmit power control of the transmission apparatus when thecommunication method is switched.

In this manner, the transmit power control of the transmission apparatusis performed when the communication method is switched, and thereby itbecomes possible to prevent an error from occurring in the communicationand also to reduce influence to another cell due to the transmission ofunnecessary power.

(2) Further, the wireless communication system of the present inventionperforms the transmit power control of the transmission apparatusaccording to communication characteristic change caused when thecommunication method is switched.

In this manner, the transmit power control of the transmission apparatusis performed according to the communication characteristic change causedwhen the communication method is switched, and thereby it becomespossible to cause the system to receive little influence of thecommunication characteristic change between before and after thecommunication method is switched.

(3) Further, in the wireless communication system of the presentinvention, the reception apparatus transmits control information forperforming the transmit power control of the transmission apparatus tothe transmission apparatus when the communication method is switched andthe transmission apparatus determines a transmitted power according tothe control information.

In this manner, the reception apparatus transmits the controlinformation for performing the transmit power control to thetransmission apparatus when the communication method is switched, andthereby it becomes possible to perform the transmit power control in aclosed loop method.

(4) Further, in the wireless communication system of the presentinvention, the transmission apparatus determines the transmitted poweraccording to the control information and information indicating whetherthe communication method has been switched or not.

In this manner, the transmission apparatus determines the transmittedpower according to the control information and the information whetherthe communication method has been switched or not, and thereby thetransmission apparatus can take a different transmit power control valueaccording to the information indicating whether the communication methodhas been switched or not even when the same control information has beentransmitted from the reception apparatus. As a result, new controlinformation needs not be used and it becomes possible to improvethroughput.

(5) Further, in the wireless communication system of the presentinvention, the transmission apparatus determines the transmitted poweraccording to a value specified for each of the transmission apparatuseswhen the communication method is switched.

In this manner, the transmission apparatus determines the transmittedpower according to the value specified for each of the transmissionapparatuses when the communication method is switched, and thereby itbecomes possible to perform the transmit power control in an open loopmethod.

(6) Further, in the wireless communication system of the presentinvention, the plural kinds of communication method are different fromone another in an access method.

By this configuration, the transmit power control of the transmissionapparatus is performed when the access method is switched, and therebyit becomes possible to prevent an error from occurring in thecommunication and also to reduce influence given to another cell due tothe transmission of unnecessary power.

(7) Further, in the wireless communication system of the presentinvention, the access method includes at least two of OFDMA (OrthogonalFrequency Division Multiple Access), DFT-S-OFDMA (Discrete FourierTransform-Spread-Orthogonal Frequency Division Multiple Access), andClustered DFT-S-OFDMA.

By this configuration, the transmit power control of the transmissionapparatus is performed when the access method is switched, and therebyit becomes possible to prevent an error from occurring in thecommunication and also to reduce the influence to another cell due tothe transmission of unnecessary power.

(8) Further, in the wireless communication system of the presentinvention, the plural kinds of communication method are different fromone another depending on whether transmission diversity is used or notor depending on a kind of the transmission diversity.

In this manner, the transmit power control of the transmission apparatusis performed when the use of the transmission diversity or the kind ofthe diversity is switched, and thereby it is possible to prevent anerror from occurring in the communication and also to reduce theinfluence to another cell due to the transmission of unnecessary power.

(9) Further, in the wireless communication system of the presentinvention, the plural kinds of communication method are different fromone another depending on the number of antennas to be used.

By this configuration, the transmit power control of the transmissionapparatus is performed when the number of the transmission antennas isswitched, and thereby it is possible to prevent an error from occurringin the communication and also to reduce the influence to another celldue to the transmission of unnecessary power.

(10) Further, a base station apparatus of the present invention, whichperforms wireless communication with a mobile station apparatus whileswitching plural kinds of communication method, transmits controlinformation for performing transmit power control of the mobile stationapparatus to the mobile station apparatus when switching thecommunication method is.

By this configuration, the control information for performing thetransmit power control of the transmission apparatus is transmitted tothe transmission apparatus when the communication method is switched,and thereby it becomes possible to perform the transmit power control inthe closed loop method.

(11) Further, a mobile station apparatus of the present invention, whichperforms wireless communication with a base station apparatus whileswitching plural kinds of communication method, receives controlinformation for performing transmit power control from the base stationapparatus when the communication method is switched and determines atransmitted power according to the control information.

By this configuration, the control information for performing thetransmit power control is received from the base station apparatus whenthe communication method is switched and the transmitted power isdetermined according to the control information, and thereby it becomespossible to perform the transmit power control in the closed loopmethod.

(12) Further, a communication method of the present invention, in whicha transmission apparatus and a reception apparatus both capable of usingplural kinds of communication method perform wireless communicationwhile switching the communication methods, performs transmit powercontrol of the transmission apparatus when the communication method isswitched.

In this manner, the transmit power control of the transmission apparatusis performed when the communication method is switched, and thereby itbecomes possible to prevent an error from occurring in the communicationand also to reduce the influence to another cell due to the transmissionof unnecessary power.

ADVANTAGE OF THE INVENTION

According to the present invention, even when the transmission methodincluding an access method is changed, it is possible to appropriatelyperform the transmit power control and to prevent throughput degradationof a whole cell. Further, it is possible to minimize the exchange ofcontrol information required for the transmit power control.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a schematic configuration of atransmission apparatus provided in a mobile station apparatus accordingto the present embodiment.

FIG. 2 is a block diagram showing a schematic configuration of abasestation apparatus according to the present embodiment.

FIG. 3A is a diagram showing TPC command generation timing.

FIG. 3B is a diagram showing access method switching timing.

FIG. 3C is a diagram showing TCP control data generation timing.

FIG. 4A is a diagram showing TPC command generation timing.

FIG. 4B is a diagram showing access method switching timing.

FIG. 4C is a diagram showing TPC control data generation timing.

BEST MODES FOR CARRYING OUT THE INVENTION

While an uplink transmitting data from a mobile station apparatus to abase station apparatus will be described for explaining the presentinvention, obviously the present embodiment can be applied to a downlinktransmitting data from the base station apparatus to the mobile stationapparatus. Further, the present embodiment assumes an access method inwhich terminals access the base station apparatus using respectivefrequencies different from one another, and assumes that pluralsubcarriers are grouped into a resource block (hereinafter, called RB)and an access band is determined for each of the groups in the assumedaccess method. Accordingly, one RB or plural RBs are used in each of theaccess methods. Further, in first and second embodiments to be explainedin the following, it is assumed that the number of transmission antennasto be used is one.

First Embodiment

Hereinafter, a first embodiment of the present invention will beexplained with reference to the drawings. FIG. 1 is a block diagramshowing a schematic configuration of a transmission apparatus providedin a mobile station apparatus according to the present embodiment. Notethat, for simple explanation, FIG. 1 shows a minimum number of blocksnecessary for explaining the present invention. Scramble unit 100provides scrambling for adding a random property to input data or foradding confidentiality to the data. A modulation unit 101 performsmodulation such as QPSK. A DFT unit 102 performs DFT for plural units ofdata. A selection unit 103 selects an output of the DFT unit 102 or anoutput of the modulation unit 101 according to control information A.The control information A is determined according to an access methodnotified by a base station apparatus.

When the selection unit 103 selects a signal output from the modulationunit 101, an OFDM signal generation unit 105 generates an OFDM signal.On the other hand, when a signal output from the DFT unit 102 isselected, the OFDM signal generation unit 105 generates a DFT-S-OFDMsignal. A resource map unit 104 allocates data to a RB to be used.

When the RBs to be used are continuous in the resource map unit 104 andthe selection unit 103 selects the output of the DFT unit 102, the OFDMsignal generation unit 105 generates the DFT-S-OFDM signal. On the otherhand, when the RBs to be used are discrete in the resource map unit 104and the selection unit 103 selects the output of the DFT 102, the OFDMsignal generation unit 105 generates a Clustered DFT-S-OFDM signal.Accordingly, in the transmission apparatus shown in FIG. 1, the threeaccess methods, OFDMA, DFT-S-OFDMA, and Clustered DFT-S-OFDMA can beswitched therebetween.

FIG. 2 is a block diagram showing a schematic configuration of abasestation apparatus according to the present embodiment. In FIG. 2, areception apparatus 200 receives a signal from a mobile stationapparatus. A received power estimation unit 201 calculates receivedpower from each of the mobile station apparatuses. A TPC control datageneration unit 202 generates data for performing TPC. A transmissionapparatus 203 transmits data and control data necessary for the TPC tothe mobile station apparatus. A mobile station control data generationunit 204 generates data controlling the mobile station apparatus.

This mobile station control data generation unit 204 determinesallocation of the RB, the access method, and the like, other than theTPC control data for each of the mobile station apparatuses, to generatethe control data. The TPC control data generation unit 202 generates aTPC command for each of the mobile station apparatuses and notifies theTPC command to the mobile station control data generation unit 204, themobile station control data generation unit 204 generates data for theTPC control when the TPC command has been notified, and the transmissionapparatus 203 notifies the TPC control data to the mobile stationapparatus.

FIG. 3A is a diagram showing TPC command generation timing. FIG. 3B is adiagram showing access method switching timing, and FIG. 3C is a diagramshowing TPC control data generation timing. In FIG. 3A to FIG. 3C, thehorizontal axis shows time and the value expressed in dB shows a TPCcontrol amount. The access method switching timing shows timing beforeand after which the access method to be used is different. Aconventional TPC control data generation timing is generated in the sameperiod as the TPC command generation timing. On the other hand, in thepresent embodiment, the TPC control data is generated in considerationof the access method switching timing.

As far as communication is not affected, the period of the TPC commandgeneration timing is preferably longer. This is because the number ofTPC control data transmissions can be reduced when the period is longerand degradation of throughput by the increase of the control data can beprevented. Further, this also because, when excessive response isperformed for an instant temporal change in a case such as one in whichthe TPC control is performed according to received power, characteristicdegradation sometimes caused by a shift from the transmission period ofthe control data.

Next, for an advantage of generating the TPC control data inconsideration of the access method switching timing, there will bedescribed an example in which the access method is switched fromClustered DFT-S-OFDMA (called Method 1) to DFT-S-OFDMA (called Method2). First, respective features of Method 1 and Method 2 will bedescribed. Method 1 and Method 2 are exactly the same in a basiccharacteristic of the communication method, while different only inwhether the RBs to be used are “discontinuous” or “continuous”. Notethat Method 1 has a possibility of selecting a RB having a higheraccuracy since the RBS can be arranged discretely, and Method 1 providesa better reception characteristic when the same mobile apparatustransmits data in the same transmitted power using both of the accessmethods.

Further, each of Method 1 and Method 2 has a problem that, whenfrequency-selective fading occurs in a propagation path to be used, ISI(inter-symbol Interference) is caused to degrade the characteristicunless a special reception apparatus is used. In the case of DFT-S-OFDM,when frequency variation is large in the propagation path, the influenceof the ISI tends to become large, but Method 1 can suppress theinfluence of the ISI compared to Method 2 since Method 1 can select acomparatively preferable RB. Note that, while Method 2 is provided witha feature of having a preferable PAPR (Peak to Average Power Ratio)characteristic for a time domain signal, the PAPR characteristic isdegraded in Method 1 compared to Method 2. This affects maximumtransmitted power in an actual system. That is, when the sametransmission apparatus is used, it is possible to increase the maximumtransmitted power in method 2 compared to Method 1.

Next, an advantage of the present embodiment will be described. Whilethe above paragraph shows that Method 1 and Method 2 are different fromeach other in the reception characteristic and Method 1 is superior toMethod 2 when communication is performed by the use of the sametransmitted power, the difference is defined as X (dB) in the presentembodiment. This X (dB) means that Method 2 needs the transmitted powerhigher than the transmitted power of Method 1 by X (dB) for obtainingthe same reception characteristic as the Method 1. Then, unless the TPCis performed at timing when the access method is switched from Method 1to Method 2, this X dB becomes a degradation of the receptioncharacteristic. That is, this timing is controlled according to thetiming shown in FIG. 3C. As described above, the conventional TPC isperformed according to the received power or the like, and thereby, whenthe instant temporal change of the received power is followed, thecharacteristic is sometimes degraded adversely, but this access methodchange, when not followed instantly, causes the degradation of thereception characteristic in X (dB) in average.

While this example shows a method of adding the timing of generating theTPC control data also at the access method switching timing in additionto the TPC command generation timing, there is devised a method in whichthe access method switching timing is made the same as the TPC controldata generation timing.

FIG. 4A is a diagram showing TPC command generation timing, FIG. 4B is adiagram showing access method switching timing, and FIG. 4C is a diagramshowing TPC control data generation timing. Note that, in the case shownin FIG. 4A to FIG. 4C, the TPC control data needs to be generated inconsideration of X (dB) in addition to a TPC control amount Y(dB)generated at the TPC command generation timing.

While the case in which the access method is switched from Method 1 toMethod 2 is described in detail hereinabove, a similar advantage can beobtained for the case in which the access method is switched from OFDMA(called Method 3) to Method 2. This is because the receptioncharacteristic is different between Method 3 and Method 2 when thetransmission is performed by the use of the same transmitted power, and,comparing Method 3 and Method 2 to each other, Method 3 has an advantagesuch as one that the ISI is not caused, in addition to an advantage thatthe RBs are used discretely and a RB having a high accuracy can beselected. The reception characteristic difference between Method 3 andMethod 2 is larger than the reception characteristic difference betweenMethod 1 and Method 2.

Next, the more detailed control will be explained. The TPC includesbroadly divided two methods; the TPC by the closed loop which controlsthe transmitted power according to the control information notified bythe base station apparatus as shown in the present embodiment and theTPC by the open loop which the mobile station apparatus estimates anattenuation amount using a distance from the base station apparatus orthe like and the mobile station apparatus controls the transmittedpower. These two methods are used together, and the following formulawill be shown as a method of determining the transmitted power.

Transmitted power=Min{Maximum transmitted power, OpTx+ClTx}  (1)

In Formula (1), OpTx is transmitted power to be determined in each ofthe mobile station apparatuses, and ClTx is a transmitted powercorrection value notified by the base station apparatus. Further, ClTxis provided by plural notification methods, a method notifying adifference from OpTx, a method of accumulating notified ClTx, a methodcombining these methods, and the like. In Formula (1), Min is a functionselecting the minimum value among the values shown in {}.

In Non-patent document 1, when the method of accumulating ClTx is used,two bits are allocated to the TPC control data, four kinds of case, −1,0, 1, and 3 (dB) can be utilized. Each of these values shows an increaseor decrease from a current transmitted power. When the influence of theaccess method switching is not provided by these values, for example,when a value of −3 dB or 5 dB is required, new data needs to beallocated for the control (three or more bits are allocated for a casecurrently expressed by two bits). Further, a system using three or moreaccess methods requires further more control data and there arises acase requiring an increased control data amount.

For preventing such increase in the control data amount, if this TPCcontrol amount notified by the base station apparatus is recognized tobe a different value at the timing when the switching of the accessmethod occurs, new control information needs not to be prepared. It isshown how to interpret the two bits for the TPC shown in Non-patentdocument 1, depending on whether the access method switching is notifiedor not. Here, each of X and Z in the table is a positive number and allthe numerical values in the table is expressed in dB.

TABLE 1 Method Method Without switching switching TPC control method(Case of (Case of bit switching FIGS. 3A to 3C) FIGS. 4A to 4C) 00 −1 −X−1 ± X  01 0 −Z ±X 10 1 Z 1 ± X 11 3 X 3 ± X

In this manner, even when the same TPC control information istransmitted from the base station apparatus, the appropriate TPC controlcan be performed by way of determining whether the access method hasbeen switched or not in the mobile station apparatus and interpretingthe TPC control value as a different value. While the method ofnotifying the control information is most easily devised as a method fornotifying the switching of the access method, whether DFT-S-OFDM orClustered DFT-S-OFDM is determined depending on whether the RBarrangement to be used is discontinuous or continuous and thereby, ifthe access method is determined depending on “continuity” of the RBsnotified by the base station, the control information needs not be newlynotified. Note that the modification shown here is an example andvarious values can be determined when a system specification isdetermined.

In Non-patent document 1, when ClTx is defined to be a difference fromOpTx, two bits are allocated to the TPC control data and four kinds ofcase, −4, −1, 1, and 4 (dB), can be utilized. These values are controldata notified at the same time when the RB is allocated to the mobilestation apparatus. It is possible to add the transmitted powerdifference by the access method switching to this control, and, in thiscase, interpretation corresponding to Table 1 becomes as shown in Table2.

TABLE 2 Without Method Method TPC control method switching switching bitswitching 1 2 00 −4 −X −4 ± X 01 −1 −Z −1 ± X 10 1 Z  1 ± X 11 4 X  4 ±X

Further, if it is permitted that the influence to another cell isincreased by the delay of the TPC control, there is also devised amethod in which the TPC control is performed only when the access methodis switched from Method 1 or 3 to Method 2, that is, when the accessmethod is switched from an access method having a preferable receptioncharacteristic to an access method having less-preferable receptioncharacteristic. Further, in the above case, there is also devised amethod which uses originally defined TPC control values and uses amaximum shift amount (“11” in Table 1) thereof. In this case, 3 dB isselected for the case of Table 1 and 4 dB is selected for the case ofTable 2. “±” in each of the Table 1 and Table 2 needs to be determinedby the mobile station apparatus, and “+” is selected when the accessmethod is switched from Method 1 or 3 to Method 2, and “−” is selectedin the reverse case.

Second Embodiment

While the first embodiment shows the method of appropriately control thetransmitted power by the closed loop when the transmitted power iscontrolled in response to the switching of the access method, thepresent embodiment shows a method of controlling the transmitted powerby the open loop (in an open loop manner). As shown also in the firstembodiment, there is devised a method of generally determining thetransmitted power as shown in the following formula as a method ofdetermining the transmitted power.

Transmitted power=Min{Maximum transmitted power, OpTx+ClTx}  (1)

In Formula (1), OpTx is transmitted power to be determined in each ofthe mobile station apparatuses, and ClTx is a transmitted powercorrection value notified by the base station apparatus. In the presentembodiment, the transmitted power is further determined by the followingformula in consideration of the switching of the access method.

Transmitted power=Min{Maximum transmitted power,(OpTx+AcOpTx)+ClTx}  (2)

AcOpTx is not a value notified by the base station apparatus but a valueto be determined by the mobile station apparatus from the specifiedaccess method. For example, when the access method is switched fromMethod 1 (Clustered DFT-S-OFDM) to Method 2 (DFT-S-OFDM), if a receptioncapability difference is X (dB) as in the first embodiment, AcOpTx isexpressed by the following formula.

AcOpTx=±X/2   (3)

For “±”, “+” is selected for the switching from Method 1 to Method 2 and“−” is selected in the reverse transition. Further, AcOpTx also can beexpressed as follows.

$\begin{matrix}\begin{matrix}{{AcOpTx} = {X\left( {{in}\mspace{14mu} {Method}\mspace{14mu} 2} \right)}} \\{= {0\left( {{in}\mspace{14mu} {Method}\mspace{14mu} 1} \right)}}\end{matrix} & (4)\end{matrix}$

An advantage over the first embodiment is that it is not necessary tochange the control of the base station apparatus and the existing TPCcontrol data and the TPC may be set only by the mobile station apparatusin response to the switching of the access method. The second embodimentalso has the same advantage as the first embodiment such as one that thereception characteristic is not degraded by the switching of the accessmethod and the influence to another cell is suppressed. Obviously, thesecond embodiment can be applied to the switching not only between theMethods 1 and 2 but also between OFDMA (Method 3) and Method 2 as thefirst embodiment. Further, the case of using more than three methods tobe switched can be easily accommodated by means of applying Formula (4).

Third Embodiment

While each of the first and second embodiments shows the case of theaccess method switching as a case of the communication method switching,the present embodiment shows respective cases in which the number oftransmission antennas to be used and a transmission diversity mode areswitched. First, the case of switching the number of transmissionantennas will be described. Both of the method of the first embodimentwhich performs the control on the base station apparatus side and themethod of the second embodiment which performs the control on the mobilestation apparatus side can be applied also to the case in which thenumber of the transmission antennas is switched, and the presentembodiment shows a case in which the control is performed on the mobilestation apparatus side as in the second embodiment.

While, in the transmission from the mobile station apparatus side by theuse of the plural antennas, there are advantages over to a case of usinga single antenna such as an advantage that maximum transmitted power isincreased, an advantage that the transmission antenna diversity can beapplied, and an advantage that a transmittable area for a base stationapparatus is increased, but, on the other hand, there is a disadvantagethat power consumption is increased. Accordingly, there is devised acommunication method of performing the control of reducing the number ofantennas to be used as far as possible and increasing the number ofantennas when communication efficiency is degraded. On the basis of suchcontrol, the present embodiment first shows a transit power controlmethod according to the increase and decrease in the number of antennasto be used. The number of antennas to be used is assumed to be 1, 2, or4. This is an example of the number of antennas to be used, for simplyexplaining the embodiment. The present embodiment is not limited to thisnumber.

There is devised a method of generally determining the transmitted poweras shown in the following formula.

Transmitted power=Min{Maximum transmitted power, OpTx+ClTx}  (1)

In Formula (1), OpTx is transmitted power to be determined in each ofthe mobile station apparatuses, and ClTx is a transmitted powercorrection value notified by the base station apparatus. In the Presentembodiment, the transmitted power is further determined by the followingformula in consideration of the switching of the number of the antennasto be used.

Transmitted power=Min{Maximum transmitted power,(OpTx+NmOpTx(n))+ClTx}  (5)

NmOpTx is not a value notified by the base station apparatus but a valuedetermined from the number of antennas n used by the mobile stationapparatus. Formula (1) is expressed in dB and a control value accordingto the number of antennas to be used is determined as Formula (6).

$\begin{matrix}\begin{matrix}{{{NmOpTx}(n)} = {{- 6}\left( {{{when}\mspace{14mu} n} = 4} \right)}} \\{= {{- 3}\left( {{{when}\mspace{14mu} n} = 2} \right)}} \\{= {0\left( {{{when}\mspace{14mu} n} = 1} \right)}}\end{matrix} & (6)\end{matrix}$

Note that, when ClTx is also controlled according to a power reachingthe base station apparatus, the correction value notified by the basestation apparatus needs to be controlled depending on the number ofantennas. By such control, the transmitted power is appropriatelycontrolled without notification from the base station apparatus andwithout notification to the base station apparatus for the number oftransmission antennas to be used.

Further, while data is transmitted from the plural antennas in the sametransmitted power in the case of Formula (5), different transmittedpower may be used for each of the antennas by way of defining a valuesuch as in Formula (5) for each of the antennas.

While the embodiment has been described so far by assuming that simplythe same data is transmitted also when the plural antennas are used,actually, when the plural antennas are used, more efficientcommunication can be performed by using a transmission diversitytechnique. “Efficient” means that a gain is obtained by encoding of thetransmission signal in addition to the advantage that the transmittedpower can be increased. That is, this means that reception capability isbetter in the case of using the transmission diversity than in the caseof simply transmitting the same data when the same power is received.This difference is defined as a transmission diversity gain. Consideringthis transmission diversity gain, Formula (5) is changed as Formula (7).

Transmitted power=Min{Maximum transmitted power,(OpTx+NmOpTx(n)+TDOpTx(n))+ClTx}  (7)

TDOpTx(n) is not a value notified by the base station but a valuedetermined from the number of transmission antennas n to be used by themobile station apparatus. When n=1, the diversity cannot be used andNmOpTx=0.

Further, there is devised a case of using plural transmission diversitymethods. This is because, since gain or loss is different depending onthe transmission diversity, the capability of the whole system can beimproved when the different transmission diversities are used dependingon a communication environment.

In this case, TDOpTx may be a function depending on the two parametersof the number of antennas n and the transmission diversity method m.That is, Formula (7) is changed as Formula (8).

Transmitted power=Min{Maximum transmitted power,(OpTx+NmOpTx(n)+TDOpTx(n,m)))+ClTx}  (8)

Further, while the maximum transmitted power is not changed in theformulae determining the transmitted power in the second and thirdembodiments, Formulae (2), (7), and (8), this value also needs to bechanged. This is because, when the access method is switched to adifferent one, back-off (value indicating how much lower value from asaturation region of a transmission amplifier can reduce the influencethereof to the signal) presumed for each access method is different. Forexample, if the back-off is different by Pbl (dB) between DFT-S-OFDMusing the continuous RBs and Clustered DFT-S-OFDM using thediscontinuous RBs, Formula (2) is changed as the following formula.

Transmitted power=Min{Maximum transmitted power−Pbl×k,(OpTx+AcOpTx)+ClTx}  (2′)

Here, k is a parameter depending on the access method, and equal to zerofor DFT-S-OFDM and equal to one for Clustered DFT-S-OFDM.

Further, when SFBC (Space Frequency Block Coding) is applied to theDFT-S-OFDM signal as the transmission diversity, the required back-offis different for each of the transmission antennas. When the antennanumber is denoted by #n and the back-off amount for each of the antennais denoted by Pb(#n), Formulas (7) and (8) are changed as the followingformulas, respectively.

Transmitted power (#n)=Min{Maximum transmitted power−Pb(#n),(OpTx+NmOpTx(n)+TDOpTx(n))+ClTx}  (7′)

Transmitted power (#n)=Min{Maximum transmitted power−Pb(#n, m),(OpTx+NmOpTx(n)+TDOpTx(n, m))+ClTx}  (8′)

Here, the transmitted power is a function of #n and m in Formulae (7′)and (8′) because the back-off amount is different for each of theantennas and resultantly the transmitted power is different sometimesfor each of the antennas.

BRIEF EXPLANATION OF REFERENCE NUMERALS

100 Scramble unit

101 Modulation unit

102 DFT unit

103 Selection unit

104 Resource map unit

105 OFDM signal generation unit

200 Reception apparatus

201 Received power estimation unit

202 TPC control data generation unit

203 Transmission apparatus

204 Mobile station control data generation unit

1-19. (canceled)
 20. A wireless communication system, in which atransmission apparatus and a reception apparatus both capable of using aplurality of kinds of communication method perform wirelesscommunication while switching the communication method, wherein transmitpower control of said transmission apparatus is performed according tomaximum transmitted power, a transmit power control value in an openloop, and a transmit power control value in a closed loop, and saidreception apparatus does not notify new information regarding thetransmit power control before and after said communication method isswitched and said transmission apparatus performs the transmit powercontrol by changing at least one of said maximum transmitted power, thetransmit power control value in the open loop, and the transmit powercontrol value in the closed loop.
 21. The wireless communication systemaccording to claim 20, wherein said plurality of communication methodsincludes at least two of OFDMA (Orthogonal Frequency Division MultipleAccess), DFT-S-OFDMA (Discrete Fourier Transfolin-Spread-OrthogonalFrequency Division Multiple Access), and Clustered DFT-S-OFDMA.
 22. Thewireless communication system according to claim 21, wherein saidtransmission apparatus judges the switching of the communication methodby how frequency to be used is allocated in a notification from thereception apparatus.
 23. The wireless communication system according toclaim 21, wherein said maximum transmitted power is controlled whenthere is a difference of a PAPR characteristic between the communicationmethods to be switched.
 24. The wireless communication system accordingto claim 21, wherein the control value in said closed loop isinterpreted as a different value when there is a difference of frequencyvariation in a propagation path between the communication methods to beswitched.
 25. The wireless communication system according to claim 20,wherein said plurality of communication methods includes use or non-useof transmission diversity or the kind of transmission diversity, and thetransmit power control value in said open loop is changed between beforeand after the use and non-use of the transmission diversity or the kindof transmission diversity are switched.
 26. The wireless communicationsystem according to claim 20, wherein said plurality of kinds ofcommunication method includes a plurality of numbers of antennas to beused, and the transmit power control value in said open loop is changedbetween before and after the number of the antennas is switched.